This invention relates to a method of vacuum depositing a layer on a substrate of a plastic film, and more particularly relates to the method suitable for continuously depositing a layer on a film in a continuous manner while the film is transported in a longitudinal direction.
During the deposition process, the temperature of the substrate is raised to a fairly high degree by the radiant heat from an evaporation source, the latent heat due to the deposition of an evaporated substance, etc. Therefore, when the plastic film is used as the substrate for the deposition, it is necessary to control the temperature of the film so as not to exceed a given value, thereby avoiding thermal damage of the film.
In order to control the temperature of the film, there has been employed a method wherein the film is transported along the peripheral surface of a metal cylinder, i.e. a can, and the evaporated substance is controlled so as to be deposited on the opposite portion of the film when it is in contact with the metal surface, so that the heat in the film is dissipated through the metal can by heat conduction.
However, the cooling effect due to the conductivity of the heat through the metal can has not been sufficient to avoid thermal damage of the film in situations where a high melting point metal is deposited into a fairly thick layer, or the deposition rate is high or the thickness of the substrate film is fairly small.